Besides the algorithmic problems ("Intermodal aus algorithmischer Sicht"), why are there not yet intermodal travel information systems which deserve this description?

The reason is partly that every supplier can only claim a part of the resulting business value. For that reason they try to establish partnerships which then don't allow for all possible options to be displayed free of discrimination (for example, car sharing with Moovel and qixxit). We doubt that, in this way, information systems will ever be created which are optimized in relation to all possible options on the market. 

But there is another reason that free of discrimination, intermodal systems cannot emerge: Normally there is no free access to public transport timetables and real-time data or none which is free of discrimination even though we can observe a slow and careful move towards OpenData. Germany, to say the least, is not a pioneer in this respect (see list below). The result is an environmental and economic disadvantage for the entire society because the proven benefits of OpenData cannot be used (Konrad Adenauer Stiftung - "Open Data - the benefits"Technologische Stiftung Berlin - "Digitales Gold"). 

This does not sound too positive, but we can try to consider the enormous opportunities of intermodal systems. Intermodal systems are a pure algorithmic supplement to already existing multimodal systems. They make sense because they find better solutions by recombining partial solutions of existing systems. They do not need an additional infrastructure, they do not need new, additional or different transport options. They only need, as an essential requirement, access to the data of various transport options, which specifically means access to the timetables of public transport companies.

This data is already available in the systems of the suppliers, and various national and EU standards for data exchange already exist. Data is exchanged in many cases already but mostly between public transport systems which the public authorities (i.e. primarily national railway associations and regional transport associations) either own or for which they have responsibility. Therefore, it should also be the responsibility of public authorities or politicians to create the requirements for free of discrimination intermodal travel information systems by allowing free of discrimination access to public transport data. Ideally this could be achieved with the supplementary creation of competition between such systems for faster realization of environmental and economic benefits for the society. Other countries are proceeding in this respect as good examples.  

The following is a list of a selection of countries worldwide using OpenData in the sequence of best score of usage with rank in parenthesis:

Australia (1), Taiwan (1), France (3), UK (3), Canada (5), Denmark (6), Brazil (7), USA (9), Latvia (9), Colombia (12), Japan (13), Mexico (16), Finland (16), Argentina (2), Sweden (20), Germany (22), Belgium (24), Ukraine (24), Slovania (24), Austria (24), ... Myanmar (94)

Source: Global Open Data Index